Overload torque clutch

ABSTRACT

An overload torque clutch in which a pair of slidable fingers on a driving member engage rigidly mounted stops on a coaxially mounted driven member. The slidable fingers are held in the engaged position by a transverse resiliently loaded yoke member which locates in specially designed recesses in the fingers. At a predetermined torque level of the fingers are forced out of contact with the stops and the yoke rides out of the recesses against the action of the resilient loading. The clutch may be reset manually, hydraulically or pneumatically. The device is particularly useful as a safety clutch to disengage heavy-duty equipment, such as conveyor belt systems, from an electric drive in the event of jamming or the like.

waited States Patent Faulds Feb. 22, 1972 [54] OVERLOAD TORQUE CLUTCH[72} Inventor: William W. Faulds, RR. 3, St. Catharines,

Ontario, Canada [22} Filed: Nov. 16, 1970 [21] Appl.No.: 89,684

FOREIGN PATENTS OR APPLlCATIONS 1,350,808 12/1963 France 192/56 RPrimary Examiner-Allan D. Herrmann Attorney weir, Marshall, MacRae &Lamb [5 7] ABSTRACT An overload torque clutch in which a pair ofslidable fingers on a driving member engage rigidly mounted stops on acoaxially mounted driven member. The slidable fingers are held in theengaged position by a transverse resiliently loaded yoke member whichlocates in specially designed recesses in the fingers. At apredetermined torque level of the fingers are forced out of contact withthe stops and the yoke rides out of the recesses against the action ofthe resilient loading. The clutch may be reset manually, hydraulicallyor pneumatically. The device is particularly useful as a safety clutchto disengage heavy-duty equipment, such as conveyor belt systems, froman electric drive in the event of jamming or the like.

7 Claims, 6 Drawing Figures PAIENTEDFEB22 I972 3.643 770 SHEET 2 UF 3 mmain" OVERLOADTORQUECLUTCII This invention relates to an overload torqueclutch, particularly for use with electric motor driven devices, such asconveyor belt systems and heavy-duty equipment, whereby drive to thebelt may be disengaged quickly and efficiently when torque in excess ofa predetermined value is applied. The device is particularly usefulwhere torque loads in excess of about 9,000 ft./lb. are encountered.

Previously known torque limiting clutches have various undesirablecharacteristics. A fault commonly found is that the limiting torquewhich is intended to cause tripping is variable either because ofvarying degrees of frictional resistance which must be overcome beforetripping can be effected, or because the resilient member which isresponsive to the applied torque is erratic. Another common fault isthat existing clutches are subject to wear at critical point such thattripping occurs at erratic applied torque levels. Another fault which iscommon is that the torque transmitting element or the torque responsiveelement is subject to breakage upon the sudden application of a torquesubstantially greater than the intended maximum torque so that extremelyheavy equipment is required and such equipment is cumbersome to operate,build, maintain and above all to reset after a stoppage. It is,therefore, one object of the present invention to provide an overloadtorque clutch which can be used in heavy-duty applications and which atleast substantially overcomes the disadvantages of the clutches of theprior art.

It is another object of the invention to provide a simple overloadtorque clutch which can be rapidly reset following application of anoverload torque by manual, hydraulic or pneumatic means.

It is yet another object to provide an overload torque clutch in which asimple sleeve bearing suffices between the coaxially aligned drivingmember and driven member because relative movement between said membersonly occurs in a no-load condition.

In order to achieve the objects of the invention there is provided, byone aspect of the invention, rotary coaxially aligned driving and drivenmembers which are releasably interconnected by a pair of stop membersrigidly mounted on said driven member and a pair of finger membersslidably mounted on said driving member. The finger members are held inan extended position in which they contact said stop members, by meansof a spring loaded yoke member located in a shaped transverse grooveadjacent the end of said finger members remote from said stop members.The yoke member is held in the groove by the action of a resilient meanssuch as a spring acting perpendicular to the movement of the fingermembers. When an overload torque is applied, the finger members areforced inwardly from the interconnecting position in contact with thestop members, and at the same time the yoke member is forced out of theshaped groove against the action of the spring so that the yoke fingersride up onto the main body of the fingers, into a disengaged or safeposition. To reset the clutch the fingers are manually hydraulically orpneumatically forced outwardly to reengage with the stop members and theyoke fingers ride back into the grooves under the action of the spring.

The invention will be more fully understood and the advantages thereofmore apparent when considered in the light of the following detaileddescription and the drawings in which:

FIG. I is a plan view of one embodiment of the clutch of the presentinvention, with the cover removed, and with the clutch in engagedposition;

FIG. 2 is a section along line 2-2 of FIG. 1, showing the cover inplace;

FIG. 3 is a similar view of the clutch of FIG. 1 shown in disengagedposition;

FIG. 4 is a section along line 4-4 of FIG. 3, showing the clutch cover;

FIG. 5 is a plan view of an alternative embodiment of the clutch, shownin disengaged position;

FIG. 6 is a section along line 66 of FIG. 5 showing the housing andreset device.

Turning first to the embodiment shown in FIGS. 1-4, there is provided anoverload torque clutch in conjunction with a drive shaft 1 and a drivensprocket toothed or gear toothed ring 2. A driving member 3 is securedto the drive shaft 1 by a key or other suitable device such as set screw4. Driven ring 2 is secured to a circular driven member 5 by securingscrews 6 and coaxially mounted over driving member 3 with a bushing orsleeve bearing 7 therebetween. Driven member 5 is pro vided with atleast two stop blocks 8 mounted diametrically opposite each other on theperiphery thereof. Blocks 8 are provided with angled contact surfaces 9,for a purpose described hereinafter. A yoke and slide housing 10 isrigidly mounted on driving member 3 as by screws 11. Housing 10 isprovided with a pair of opposed slide channels in which finger slides 12may be advanced and retracted. Slides 12 as provided with angled endshaving an included angle of about 5060 which mate with the angledcontact faces 9 of blocks 8. A spring loaded pin 13 is also mounted inhousing 10, transverse to slides 12 and carrying a yoke 14. Yoke 14 isprovided with two arms 15 and 16 having V-shaped ends and adapted tomove in housing 10 transverse to the movement of slides 12. Yoke 14 mayflex somewhat on pin 13 and along the length so that binding may beeliminated. The V-shaped ends of arms 15 and 16 are adapted to fit inV-shaped recesses 15 and 16 in slides 12 when the slides 12 are in anextended position in which the V-shaped ends thereof may contact thesloping contact faces 9 of blocks 8. Arms 15 and 16 are held in therecesses 15 and 16 by the pressure of compression spring 17 exerted onthe yoke 14 via pin 13.

In operation, should an overload torque be applied as by a stoppage orjam on the conveyor belt driven by gear or chain sprocket wheel 2, theV-shaped ends of slides 12 are caused to ride down the sloping contactfaces 9 towards the retracted position as shown in FIG. 3. As slides 12retract, the V-shaped ends of arms 15 and 16 are forced out of recesses15' and 16', against the pressure of spring 17, so that in the positionshown in FIG. 3 the clutch is disengaged and the driving member 3rotates under no-load conditions relative to driven member 5. It will beappreciated that the overload torque at which the clutch disengages is amatter of design convenience and can be varied over a wide range byadjustment of the angles on the contact faces of the slides 12 and yokearms 15 and 16, and by adjustment of compression spring 17. Normally theangle of contact face 9 of block 8 corresponds to that of the contactfaces of slides 12 which have an included angle of between 50 and 60,and the angle of the recesses 16 is somewhat greater so that arms 15 and16 ride out of recesses 16 without difficulty. As arms 15 and 16 rideout of the recesses 16' a considerable area of contact remains at thepressure contact face 9 of block 8 and slides 12 so that when the tipsof arms 15 and 16 reach the fiat surface of the slides, the slidescontinue their inward movement to disengage from blocks 8 without riskof breakage of the tips of slides 12. Obviously, should arms 16 and 15jam in recesses 15 and 16, slides 12 would be distorted or broken byexcess pressure on faces 9 of blocks 8.

Resetting of the clutch can be effected in several ways, one of which isshown in FIGS. 2, 4, and 6. FIG. 4, for example, shows a cover 18 overthe center of the clutch provided with a bushing 19 for a plunger 21.Plunger 21 is provided with a hand button 22 and a wedge 23, which wedgecooperates with similarly shaped ends 24 of slides 12 so that anoperator merely pushes button 22 inwardly to effect extension of slides12 into cooperation with stop members 8. If desired, plunger 21 may beresiliently loaded to ensure retraction of wedge 23 out of contact withends 24 following reset, although this is not essential as plunger 21and wedge 23 are free to float out of contact. As an alternative to themanual reset a pneumatic or hydraulic reset may be employed in whichplunger 21 and button 22 are replaced by an airline which is screwedinto bushing 19 so that cover 18 acts as a hydraulic or pneumaticcylinder in which wedge 23 is a floating piston. In a furtheralternative embodiment the clutch could be electrically operated by asolenoid to actuate hand button 22.

It will be appreciated by those skilled in the art that numerousalternative embodiments of the invention may be produced, withoutdeparting from the invention and the novel characteristics of the yokeand slide arrangement described hereinbefore. For example, the clutch ofthe present arrangement may be employed with a chain drive, with a chaindrive sprocket or may be employed in a geared drive device dependingupon the driven member chosen. It will also be appreciated that theclutch of the present invention may be operated equally well in bothforward and reverse rotation without modification thereto. Alternativereset devices as herein described may be employed as specificcircumstances require. In the embodiment illustrated in FIGS. 14, arelatively deep clutch is described which is provided with a clutchcover 20 which is particularly suitable in dusty or dirty environments.In other environments or situations, the cover 20 may be omitted withoutdeparting from the essential novelty of the present invention. In yetother circumstances, a clutch such as that shown in FIGS. 1-4 may beimpractical by reason of the space available, and in such cases resortmay be had to the thinner uncovered embodiment illustrated in FIGS. 5and 6. In FIGS. 5 and 6 the driving member 3, block 10, slides 12 andyoke 14 are precisely similar to the parts of like numbers in FIGS. LA,and operate in similar manner. Driven member 5, is however, rotatablymounted around the periphery of driving member 3 on a ball race 24 suchthat the total depth of the clutch is considerably reduced asillustrated in FIG. 6. A sprocket wheel 2 and stop members 8 are securedto the driven member as before and the clutch functions as describedwith reference to FIGS. 1-4. FIG. 6 shows a cover 18 adapted to receivea bushing for a pneumatic reset device although it will be appreciatedthat the same cover may be adapted to receive a manual reset mechanismwhich operates in the same manner as that described with reference toFIG. 4.

An additional modification is illustrated in FIG. 5 inasmuch as aplurality of pairs of stop members 8 are shown in distinction to FIGS. 1to 3 where only a single pair of members 8 are shown. A plurality ofpairs of members 8 permits smoother engagement and less lost motionbefore engagement and is to be preferred in heavy load situations. Inthe embodiment shown in FIGS. 5 and 6, the ball race 24 includes a largenumber of relatively small diameter balls, but it will be appreciatedthat the number and diameter of the balls is not critical and may bevaried within wide limits depending upon the particular designsituation. It will also be noted that driving member 3 is provided witha peripheral cover plate 25, secured by screws 26, which may be removedto facilitate insertion of the ball bearings into ball race 24.

In a further alternative embodiment the clutch of the present inventionmay be air assisted. When employed, preferably with a pneumatic reset,the torque releasing point may be set at a lower torque level than isrequired to drive the load, but with sufficient tension on spring 17 tohold the clutch in the safe or disengaged position shown in FIGS. 3 and5. A regulated air pressure may be applied to the clutch reset system,and maintained at intervals, to force piston 23 inwards thus forcingslides 12 outwardly into engagement with stops 8. When the air pressureis removed the clutch will release or disengage. Thus the clutch can becontrolled by regulating the air pressure so as to provide a stop andstart" clutch with an overload protection device.

In yet another alternative mode of operation, particularly useful insituations where the initial startup torque exceeds the desired overloadtorque release point, an operator can assist the clutch by applyingpneumatic pressure to the reset at startup thereby preventing the clutchdisengaging at the preset level while still permitting release at ahigher torque in the event ofajam. The actual release point is, ofcourse, governed by the pneumatic pressure. Once the equipment isfunctioning under normal load conditions, the operator can release thepneumatic assist and the clutch then remains in engagement as describedherein before.

I claim:

1. An overload torque clutch comprising: a rotatable driving member; arotatable driven member coaxially mounted with said driving member; atleast two stop members rigidly mounted on said driven member indiametrically opposed relationship; a pair of slide members slidablymounted on said driving member for slidingly releasable engagement withsaid stop members; a yoke member having a pair ofdependent armsresiliently mounted on said driving member transverse to said slidemembers, each of said arms being adapted to releasably engage a recessformed in a respective one of said slide members whereby said slidemembers are held in releasable engagement with said stop members; andmeans mounted on said driving member to extend said slide members intoengagement with said stop members.

2. An overload torque clutch as claimed in claim 1, wherein each of saidslide members is provided with a V-shaped end having an included angleof between 50 and 60 and said stop members are provided with contactfaces having angles complementary to said V-shaped ends.

3. An overload torque clutch as claimed in claim 2 wherein each of saidarms is provided with a V-shaped end which releasably engages in acorrespondingly shaped recess provided in a respective said slide memberat a position remote from said V-shaped end thereof.

4. An overload torque clutch as claimed in claim 1 wherein said means toextend said slide members comprises a pneumatic means.

5. An overload torque clutch as claimed in claim 1 wherein said means toextend said slide members comprises a manually operated reset means.

6. An overload torque clutch as claimed in claim 1 including a covermember mounted on said driving member and on which cover member saidmeans to extend said slide members is secured.

7. An overload torque clutch as claimed in claim 1 wherein said yokemember is provided with a resilient spring means whereby said arms aremaintained in releasable engagement with said recesses.

1. An overload torque clutch comprising: a rotatable driving member; arotatable driven member coaxially mounted with said driving member; atleast two stop members rigidly mounted on said driven member indiametrically opposed relationship; a pair of slide members slidablymounted on said driving member for slidingly releasable engagement withsaid stop members; a yoke member having a pair of dependent armsresiliently mounted on said driving member transverse to said slidemembers, each of said arms being adapted to releasably engage a recessformed in a respective one of said slide members whereby said slidemembers are held in releasable engagement with said stop members; andmeans mounted on said driving member to extend said slide members intoengagement with said stop members.
 2. An overload torque clutch asclaimed in claim 1, wherein each of said slide members is provided witha V-shaped end having an included angle of between 50* and 60* and saidstop members are provided with contact faces having angles complementaryto said V-shaped ends.
 3. An overload torque clutch as claimed in claim2 wherein each of said arms is provided with a V-shaped end whichreleasably engages in a correspondingly shaped recess provided in arespective said slide member at a position remote from said V-shaped endthereof.
 4. An overload torque clutch as claimed in claim 1 wherein saidmeans to extend said slide members comprises a pneumatic means.
 5. Anoverload torque clutch as claimed in claim 1 wherein said means toextend said slide members comprises a manually operated reset means. 6.An overload torque clutch as claimed in claim 1 including a cover membermounted on said driving member and on which cover member said means toextend said slide members is secured.
 7. An overload torque clutch asclaimed in claim 1 wherein said yoke member is provided with a resilientsPring means whereby said arms are maintained in releasable engagementwith said recesses.